Today hand washing laundry is the main washing habit for developing & emerging (D&E) countries all over the world. It is also true that hand washing laundry will continue for some more decades due to socio economical reason. Especially, lower income people are the main user for hand wash laundry. In many D & E countries, hand wash laundry detergent is still available for less than one dollar per kilogram and lower income people are getting clean water at free of cost. These points are the basic reasons for continuing such laundry habit for longer time. Consumers in hand wash laundry believe that detergent producing good amount of lather during washing is the best quality detergent for removing dirt from fabrics i.e. foam quantity during the washing in hand wash laundry is very important. As a result, multiple numbers of rinsing is required during the rinsing stage for removing excessive foam from the fabrics i.e. huge amount of clean water is used during the hand wash laundry only for removing loam from rinsing water although realistically residual dirt gets removed from fabric after 1 to 2 rinses.
In hand washing process, water is taken in a bucket or in fabric's soaking container or in case of machine washing process water is taken in a washing tub in washing machine. Thereafter, desired quantity of detergent is added to generate lather by hand shaking or the washing tub in washing machine is run for a while. This is followed by immersion of the dirt fabrics for soaking for 10 to 30 min. After soaking period, the fabric is rubbed by hand to remove dirt or the washing cycle is run for 10 to 20 min in case of machines wash.
For rinsing, the dirt water is drained out and excess dirt water is removed by squeezing the fabrics. Thus each such rinsing cycle consists of squeezing the fabrics and rinsing the fabrics with fresh water. Such rinsing cycle is repeated for four to five times for hand wash or in case of machine, four to five times rinse cycle is followed to remove all foams before final spinning. It is also a fact that in some areas people are paying higher amount of price for water used in rinsing due to the fact of using high foaming detergent in hand wash laundry. It is also a fact that consumers in hand wash laundry is not only spending extra money for rinsing water or wasting clean water in rinsing stage due to foam but also spending longer laundry time to complete one hand wash laundry. It is also true that consumer in hand wash laundry can buy water for rinsing or don't care to waste clean water for rinsing but are not ready to pay additional money for hand wash detergent which delivers less water usage in rinsing.
Attempts have been made in the past to resolve this problem by secondary method, called single rinse concept where during rinsing cycle, use of a defoamer containing fabric conditioner where fabric conditioner conditions the fabric at rinsing cycle and in addition kills all the residual foam. This concept was not very much successful in case of hand washing process, since use of fabric conditioner in this class is considered to be a luxury and people of hand-washing segment uses hand washing due to money constraint for fabric cleaning.
Considering the billion tons of clean precious water wastage and sensitive formulation cost for normal detergent used in hand wash laundry or machine wash, there has been a need for detergent formulations which when used for washing fabrics most likely generates preferred amount of foaming during washing cycle without affecting the cleaning nature of the detergent but also have antifoaming activity in rinsing cycle so that one or two rinse is enough, to clean the fabric without effecting much detergent formulation cost. It is however extremely difficult to provide for such characteristics in detergent formulations which would favour both the washing and rinsing cycles and make washing of clothes/fabrics more convenient and user friendly apart from taking care of avoiding unnecessary wastage of valuable water and saving the environment from unnecessarily wastage of water in hand wash laundry and/or machine washing.
EP 0685250A1 disclosed a foam control composition which acts as a foam inhibiting agent in rinsing cycles when use in together with detergent. Table 1 therein reveals washing stage foam height from 2 cm to 9 cm for examples 1 to 4 against blank foam height 13 cm. Therefore, the washing stage foam height deterioration is strongly evident when compared to the blank that is even less than the blank in the case of this prior art composition which constitutes a major drawback or failure to meet the fundamental requirements of good foam control composition favouring same foam height as that of blank or avoiding reduction of foam quantity during the washing stage. Thus the foam control composition of EP 0685250A1 in any hand washing laundry detergent composition cannot be considered beneficial for the consumers desirous of having good foam in the washing cycle and no foaming in just after 1-2 rinse cycles.
WO2011107361A discloses a delayed antifoam composition that has a polyoxyalkylene group as the terminal group of the polyether containing aminosiloxane. The production of polyether containing amino siloxanes of WO2011107361A is expensive. In practice such materials are produced through equilibrium reaction starting from OH-terminated polydimethylsiloxanes, α, ω-polyether-functional siloxanes and hydrolysates of corresponding aminoalkylsilane. There is a major disadvantage that often in this synthesis the two-phase reaction mixture results; since, because of different polarities the polyether siloxane is not compatible with the remaining components.
DE102012210211A1 also disclosed an antifoaming agent having delayed antifoaming agent in the detergent composition. It would be found that under Examples 1-5 and comparison example in DE102012210211A1 while obliging defoaming during rinsing reveals significant percent reduction of foam during the washing process than the blank sample. Also closer comparison of [%] foam in the washing process as compared to rinse 1 process reveals that the percent foam in the washing process is lesser than the percentage of foam in the rinse 1 process which go to demonstrate that antifoaming action is more active or more inherent in the washing process than in rinsing process and hence not desirable.
It is thus apparently clear from the above state of art that the delayed antifoam in the hand wash and machine wash does not only suppress foam at the rinsing stage but also suppresses foam in the washing stage, and moreover, for certain antifoam compounds the difficulty in preparing and the involvement of high cost makes it undesirable for use in hand wash or machine wash laundry.
Thus it is a need in the art to obtain cost-effective laundry formulation that would have sufficient foam depression property in the rinsing stage without affecting the foam height during the washing stage and at the same time would also be easy to synthesize.